The Roots of Our Discontent: A Recent Ontario Court of Appeal Case Sheds New Light on Causation Analysis

By Edmund Nilson

Untangling causation is one of the perennial challenges of the law, especially in complicated matters which require expert evidence. In the recent case of Ibrahimova v. Cavanagh, 2026 ONCA 573, the Ontario Court of Appeal has provided additional guidance for approaching causation, especially in the domain of medical negligence.

Factual Background

This case arose from a previable, prelabour, preterm rupture of membranes (“pPPROM”) suffered by the respondent, Ms. Ibrahimova (the “respondent”). The respondent was in the second trimester of her first pregnancy when she experienced vaginal bleeding, lower abdominal cramps, and discharge. She attended the Kincardine Hospital’s emergency department and was seen by the appellant, Dr. Cavanagh (the “appellant”) on May 3, 2019. The respondent was diagnosed with a threatened miscarriage and sent home. The respondent was to return if her symptoms escalated.

The respondent returned to the hospital twelve hours later, on May 4, 2019, with additional bleeding and amniotic fluid discharge. She was again seen by the appellant, who diagnosed her with a threatened abortion likely to progress to a miscarriage. The plaintiff’s symptoms continued to escalate, and she saw two additional doctors, Dr. Kalaichandran and Dr. Ponesse, on May 5 and 6, respectively, who both diagnosed the plaintiff with a second trimester bleed.

On May 7, the respondent’s husband called an ambulance at approximately 2 a.m. After attending first Kincardine hospital then London Hospital, she was operated on. The pPPROM had escalated such that the plaintiff suffered septic shock, resulting in catastrophic injuries.

The case was first heard by Sproat J. at the Ontario Court of Appeal, in Ibrahimova v. Cavanagh, 2025 ONSC 4808. At the trial court, all three above doctors, Drs. Cavanagh, Kalaichandran, and Ponesse, were defendants. The trial court heard expert evidence on the issues of standard of care and causation.

The Court ultimately held that all three doctors did not meet the standard of care, but that Drs. Kalichandran and Ponesse did not cause the respondent’s injuries, as their intervention occurred after the critical juncture and were therefore not liable for damages. The appellant was held to have caused the respondent’s injuries, as the Court held that, if the appellant had met the standard of care, the respondent would have terminated the pregnancy and sought treatment, and would therefore not have suffered septic shock.

Court of Appeal

The Court of Appeal considered four grounds for appeal:

1. Whether the trial judge made findings of fact relevant to causation absent evidence that could ground them;
2. Whether the trial judge invented a new standard of obstetrical care;
3. Whether the trial judge misapplied the law of adverse inference;
4. Whether the trial judge’s approach to causation reversed the onus of proof.

On the first ground of appeal, the Court held that the trial judge had not made impermissible findings of fact relevant to causation.

The Court first stated the established law of causation, as set out by the Ontario Court of Appeal in Sacks v. Ross, 2017 ONCA 773, and Hasan v. Trillium Health Centre (Mississauga), 2024 ONCA 586. The established law provides a three step analytical framework for determining negligence that the trial judge followed:

1. First, the trier of fact is to determine what actually happened;
2. Second, the trier of fact must determine what would have happened had standard of care been met;
3. Thirdly, the trier of fact must divide responsibility between the parties, if applicable.

This framework is tempered by the Court’s decision in Goodman v. Viljoen, 2012 ONCA 896, which stresses the need to not resort to speculation or common sense when applying expert knowledge, despite the generally pragmatic nature of the causation analysis.

The appellant alleged several specific defects, including that the trial judge erred in finding that the respondent would have elected to terminate the pregnancy, that obstetricians could have identified a potential infection, that the London Hospital would have prioritized the procedure to terminate the pregnancy, and that the procedure could have been performed promptly after the respondent’s decision to proceed.

The Court rejected each of these arguments. The trial judge’s determination that the respondent would have terminated the pregnancy was made following a robust weighing of the respondent’s evidence and the available expert evidence regarding the risk of proceeding with the pregnancy. It was also properly informed by what a reasonable person would have done in the circumstances.

The determination that obstetricians would have identified a potential infection was supported by expert evidence, and at the very least it was clear that reasonable obstetricians would not have ignored a potential infection, even if all indicators for clinical diagnosis were not made out. The expert evidence likewise supported the trial judge’s finding that a procedure to address the respondent’s condition would have been treated urgently by the hospital. Finally, the trial judge had sufficient evidence to find that the procedure could have been performed promptly and, regardless, the trial judge’s finding on this matter was not determinative.

On the second ground of appeal, that the trial judge had invented a new standard of obstetrical care, the Court similarly rejected the appellants submissions. The appellant alleged that the trial judge should have determined when the respondent developed an infection and when the infection proceeded to septic shock. However, the Court held that the trial judge reasonably found, based on the available expert evidence, that the standard of care required intervention prior to a formal diagnosis of infection.

On the third ground for appeal, the Court held that the trial judge properly characterized the law of adverse inference. The appellant had sought an adverse inference based on the respondent’s failure to ask their expert witness when the respondent developed an infection and how quickly a procedure to address the respondent’s condition could have been performed. The Court held that the issue of when the infection developed was a red herring, and that the trial judge was owed deference regarding his conclusion that there was sufficient evidence to find that the procedure could have been performed promptly, notwithstanding the respondent’s failure to question their expert witness on this point.

Finally, regarding the fourth ground for appeal, the Court held that the trial judge did not reverse the onus of proof by requiring the appellant to adduce evidence. The root of the appellant’s complaints was held to be simple comments the trial judge made about the availability of evidence which had no bearing on whether the appellant was actually required to adduce said evidence.

The Court dismissed the appeal with costs, ultimately citing Brown v. Meaney, 2026 ONCA 445, for the proposition that the respondents’ merely had to show on a “common-sense basis” that the respondent’s injuries would not have occurred but for the appellant’s injuries.

Takeaways

This case represents an interesting development in the Court’s analysis of causation, especially in medical negligence cases.

Of particular importance is the Court’s recognition and elaboration of the boundaries between findings of fact that require expert evidence and findings of fact that allow for a more general analysis of reasonableness. It also reinforces the importance of pragmatism and common sense in the causation analysis.

The holding in this case demonstrates that expert evidence is not always required for conclusions that appear, at face value, to be medical determinations requiring expert evidence to substantiate, provided there is a reasonable grounding in the available evidence to draw said conclusions.

Expert evidence remains crucial: the trial judge’s holding, and the Court of Appeal’s interpretation of the trial judge’s analysis, both turned heavily on expert evidence. Expert evidence is not needed to permit reasonable, common sense inferences regarding causation, however.